During embryonic development, normal adult heart cell homeostasis and in response to cardiac injury, cardiogenesis requires the formation of muscle and non-muscle cell lineages within the myocardial tissue (1-5). Cardiac tissue development is orchestrated by the expansion and differential specification of cardiac multipotent progenitor/precursor cells (1-4). On the other hand, maintenance of cardiac cell diversity during adulthood, in response to normal wear and tear or following minor or major damages, appears to be mainly due to the activity of cardiac stem/progenitor cells (5,6). Indeed, the adult heart harbours resident and tissue-specific endogenous cardiac stem-progenitor cells (eCSCs), even though several phenotypically different cell populations with dissimilar regenerative potential have been described so far (5,7). Understanding how embryonic progenitor/precursor and adult stem/progenitor cells generate and control the formation of pacemaker, atrial and ventricular muscle cell lineages, or smooth muscle and endothelial vascular cell lineages is of fundamental importance in unravelling the molecular cues that underlie both cardiovascular development and myocardial regeneration. In particular, while a number of molecules and signalling pathways driving heart cell specification in embryonic life have been established, whether the same mechanisms (or different) are operative on adult eCSCs is largely unknown (8,9). Elucidation of factors and signalling pathways that govern eCSC self-renewal and differentiation and their mode of action, in addition to providing a better understanding of adult myocardial biology, could also make feasible the design of a cocktail of growth factors and activating molecules which could stimulate in situ the expansion and maturation of these regenerative cells (10).
To date, no one has described isolated and enriched c-kitposeCSCs, that are CD45neg, and Tryptaseneg. No one has described a reproducible method to isolate and enrich these cells to generate amounts large enough to be suitable for therapeutic purposes. The enriched population contains more than 98% of eCSCs that have these properties. No one has described the use of compositions discussed below, in the growth and differentiation of eCSCs. In particular, no one has demonstrated the use of such composition to modulate the differentiation of c-kitposeCSCs, that are CD 166pos, CD45neg, and Tryptaseneg. Likewise, no one has described the use of the compounds described herein to expand the eCSCs populations so as to produce a pharmaceutical composition containing such cells. Such expanded eCSCs cell cultures would be useful in the treatment of damaged cardiacmyogenic tissues. Because control over cardiac stem-precursor cell differentiation can produce cell populations that are therapeutically useful, there is a need for the ability to control and regulate the differentiation of cells of cardiacmyogenic lineage.